1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/kernel/profile.c 4 * Simple profiling. Manages a direct-mapped profile hit count buffer, 5 * with configurable resolution, support for restricting the cpus on 6 * which profiling is done, and switching between cpu time and 7 * schedule() calls via kernel command line parameters passed at boot. 8 * 9 * Scheduler profiling support, Arjan van de Ven and Ingo Molnar, 10 * Red Hat, July 2004 11 * Consolidation of architecture support code for profiling, 12 * Nadia Yvette Chambers, Oracle, July 2004 13 * Amortized hit count accounting via per-cpu open-addressed hashtables 14 * to resolve timer interrupt livelocks, Nadia Yvette Chambers, 15 * Oracle, 2004 16 */ 17 18 #include <linux/export.h> 19 #include <linux/profile.h> 20 #include <linux/memblock.h> 21 #include <linux/notifier.h> 22 #include <linux/mm.h> 23 #include <linux/cpumask.h> 24 #include <linux/cpu.h> 25 #include <linux/highmem.h> 26 #include <linux/mutex.h> 27 #include <linux/slab.h> 28 #include <linux/vmalloc.h> 29 #include <linux/sched/stat.h> 30 31 #include <asm/sections.h> 32 #include <asm/irq_regs.h> 33 #include <asm/ptrace.h> 34 35 struct profile_hit { 36 u32 pc, hits; 37 }; 38 #define PROFILE_GRPSHIFT 3 39 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT) 40 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit)) 41 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ) 42 43 static atomic_t *prof_buffer; 44 static unsigned long prof_len; 45 static unsigned short int prof_shift; 46 47 int prof_on __read_mostly; 48 EXPORT_SYMBOL_GPL(prof_on); 49 50 static cpumask_var_t prof_cpu_mask; 51 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS) 52 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits); 53 static DEFINE_PER_CPU(int, cpu_profile_flip); 54 static DEFINE_MUTEX(profile_flip_mutex); 55 #endif /* CONFIG_SMP */ 56 57 int profile_setup(char *str) 58 { 59 static const char schedstr[] = "schedule"; 60 static const char sleepstr[] = "sleep"; 61 static const char kvmstr[] = "kvm"; 62 const char *select = NULL; 63 int par; 64 65 if (!strncmp(str, sleepstr, strlen(sleepstr))) { 66 #ifdef CONFIG_SCHEDSTATS 67 force_schedstat_enabled(); 68 prof_on = SLEEP_PROFILING; 69 select = sleepstr; 70 #else 71 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n"); 72 #endif /* CONFIG_SCHEDSTATS */ 73 } else if (!strncmp(str, schedstr, strlen(schedstr))) { 74 prof_on = SCHED_PROFILING; 75 select = schedstr; 76 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) { 77 prof_on = KVM_PROFILING; 78 select = kvmstr; 79 } else if (get_option(&str, &par)) { 80 prof_shift = clamp(par, 0, BITS_PER_LONG - 1); 81 prof_on = CPU_PROFILING; 82 pr_info("kernel profiling enabled (shift: %u)\n", 83 prof_shift); 84 } 85 86 if (select) { 87 if (str[strlen(select)] == ',') 88 str += strlen(select) + 1; 89 if (get_option(&str, &par)) 90 prof_shift = clamp(par, 0, BITS_PER_LONG - 1); 91 pr_info("kernel %s profiling enabled (shift: %u)\n", 92 select, prof_shift); 93 } 94 95 return 1; 96 } 97 __setup("profile=", profile_setup); 98 99 100 int __ref profile_init(void) 101 { 102 int buffer_bytes; 103 if (!prof_on) 104 return 0; 105 106 /* only text is profiled */ 107 prof_len = (_etext - _stext) >> prof_shift; 108 109 if (!prof_len) { 110 pr_warn("profiling shift: %u too large\n", prof_shift); 111 prof_on = 0; 112 return -EINVAL; 113 } 114 115 buffer_bytes = prof_len*sizeof(atomic_t); 116 117 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL)) 118 return -ENOMEM; 119 120 cpumask_copy(prof_cpu_mask, cpu_possible_mask); 121 122 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN); 123 if (prof_buffer) 124 return 0; 125 126 prof_buffer = alloc_pages_exact(buffer_bytes, 127 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN); 128 if (prof_buffer) 129 return 0; 130 131 prof_buffer = vzalloc(buffer_bytes); 132 if (prof_buffer) 133 return 0; 134 135 free_cpumask_var(prof_cpu_mask); 136 return -ENOMEM; 137 } 138 139 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS) 140 /* 141 * Each cpu has a pair of open-addressed hashtables for pending 142 * profile hits. read_profile() IPI's all cpus to request them 143 * to flip buffers and flushes their contents to prof_buffer itself. 144 * Flip requests are serialized by the profile_flip_mutex. The sole 145 * use of having a second hashtable is for avoiding cacheline 146 * contention that would otherwise happen during flushes of pending 147 * profile hits required for the accuracy of reported profile hits 148 * and so resurrect the interrupt livelock issue. 149 * 150 * The open-addressed hashtables are indexed by profile buffer slot 151 * and hold the number of pending hits to that profile buffer slot on 152 * a cpu in an entry. When the hashtable overflows, all pending hits 153 * are accounted to their corresponding profile buffer slots with 154 * atomic_add() and the hashtable emptied. As numerous pending hits 155 * may be accounted to a profile buffer slot in a hashtable entry, 156 * this amortizes a number of atomic profile buffer increments likely 157 * to be far larger than the number of entries in the hashtable, 158 * particularly given that the number of distinct profile buffer 159 * positions to which hits are accounted during short intervals (e.g. 160 * several seconds) is usually very small. Exclusion from buffer 161 * flipping is provided by interrupt disablement (note that for 162 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from 163 * process context). 164 * The hash function is meant to be lightweight as opposed to strong, 165 * and was vaguely inspired by ppc64 firmware-supported inverted 166 * pagetable hash functions, but uses a full hashtable full of finite 167 * collision chains, not just pairs of them. 168 * 169 * -- nyc 170 */ 171 static void __profile_flip_buffers(void *unused) 172 { 173 int cpu = smp_processor_id(); 174 175 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 176 } 177 178 static void profile_flip_buffers(void) 179 { 180 int i, j, cpu; 181 182 mutex_lock(&profile_flip_mutex); 183 j = per_cpu(cpu_profile_flip, get_cpu()); 184 put_cpu(); 185 on_each_cpu(__profile_flip_buffers, NULL, 1); 186 for_each_online_cpu(cpu) { 187 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; 188 for (i = 0; i < NR_PROFILE_HIT; ++i) { 189 if (!hits[i].hits) { 190 if (hits[i].pc) 191 hits[i].pc = 0; 192 continue; 193 } 194 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 195 hits[i].hits = hits[i].pc = 0; 196 } 197 } 198 mutex_unlock(&profile_flip_mutex); 199 } 200 201 static void profile_discard_flip_buffers(void) 202 { 203 int i, cpu; 204 205 mutex_lock(&profile_flip_mutex); 206 i = per_cpu(cpu_profile_flip, get_cpu()); 207 put_cpu(); 208 on_each_cpu(__profile_flip_buffers, NULL, 1); 209 for_each_online_cpu(cpu) { 210 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 211 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 212 } 213 mutex_unlock(&profile_flip_mutex); 214 } 215 216 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) 217 { 218 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 219 int i, j, cpu; 220 struct profile_hit *hits; 221 222 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1); 223 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 224 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 225 cpu = get_cpu(); 226 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)]; 227 if (!hits) { 228 put_cpu(); 229 return; 230 } 231 /* 232 * We buffer the global profiler buffer into a per-CPU 233 * queue and thus reduce the number of global (and possibly 234 * NUMA-alien) accesses. The write-queue is self-coalescing: 235 */ 236 local_irq_save(flags); 237 do { 238 for (j = 0; j < PROFILE_GRPSZ; ++j) { 239 if (hits[i + j].pc == pc) { 240 hits[i + j].hits += nr_hits; 241 goto out; 242 } else if (!hits[i + j].hits) { 243 hits[i + j].pc = pc; 244 hits[i + j].hits = nr_hits; 245 goto out; 246 } 247 } 248 i = (i + secondary) & (NR_PROFILE_HIT - 1); 249 } while (i != primary); 250 251 /* 252 * Add the current hit(s) and flush the write-queue out 253 * to the global buffer: 254 */ 255 atomic_add(nr_hits, &prof_buffer[pc]); 256 for (i = 0; i < NR_PROFILE_HIT; ++i) { 257 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 258 hits[i].pc = hits[i].hits = 0; 259 } 260 out: 261 local_irq_restore(flags); 262 put_cpu(); 263 } 264 265 static int profile_dead_cpu(unsigned int cpu) 266 { 267 struct page *page; 268 int i; 269 270 if (cpumask_available(prof_cpu_mask)) 271 cpumask_clear_cpu(cpu, prof_cpu_mask); 272 273 for (i = 0; i < 2; i++) { 274 if (per_cpu(cpu_profile_hits, cpu)[i]) { 275 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]); 276 per_cpu(cpu_profile_hits, cpu)[i] = NULL; 277 __free_page(page); 278 } 279 } 280 return 0; 281 } 282 283 static int profile_prepare_cpu(unsigned int cpu) 284 { 285 int i, node = cpu_to_mem(cpu); 286 struct page *page; 287 288 per_cpu(cpu_profile_flip, cpu) = 0; 289 290 for (i = 0; i < 2; i++) { 291 if (per_cpu(cpu_profile_hits, cpu)[i]) 292 continue; 293 294 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); 295 if (!page) { 296 profile_dead_cpu(cpu); 297 return -ENOMEM; 298 } 299 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page); 300 301 } 302 return 0; 303 } 304 305 static int profile_online_cpu(unsigned int cpu) 306 { 307 if (cpumask_available(prof_cpu_mask)) 308 cpumask_set_cpu(cpu, prof_cpu_mask); 309 310 return 0; 311 } 312 313 #else /* !CONFIG_SMP */ 314 #define profile_flip_buffers() do { } while (0) 315 #define profile_discard_flip_buffers() do { } while (0) 316 317 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) 318 { 319 unsigned long pc; 320 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 321 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); 322 } 323 #endif /* !CONFIG_SMP */ 324 325 void profile_hits(int type, void *__pc, unsigned int nr_hits) 326 { 327 if (prof_on != type || !prof_buffer) 328 return; 329 do_profile_hits(type, __pc, nr_hits); 330 } 331 EXPORT_SYMBOL_GPL(profile_hits); 332 333 void profile_tick(int type) 334 { 335 struct pt_regs *regs = get_irq_regs(); 336 337 if (!user_mode(regs) && cpumask_available(prof_cpu_mask) && 338 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask)) 339 profile_hit(type, (void *)profile_pc(regs)); 340 } 341 342 #ifdef CONFIG_PROC_FS 343 #include <linux/proc_fs.h> 344 #include <linux/seq_file.h> 345 #include <linux/uaccess.h> 346 347 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v) 348 { 349 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask)); 350 return 0; 351 } 352 353 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file) 354 { 355 return single_open(file, prof_cpu_mask_proc_show, NULL); 356 } 357 358 static ssize_t prof_cpu_mask_proc_write(struct file *file, 359 const char __user *buffer, size_t count, loff_t *pos) 360 { 361 cpumask_var_t new_value; 362 int err; 363 364 if (!zalloc_cpumask_var(&new_value, GFP_KERNEL)) 365 return -ENOMEM; 366 367 err = cpumask_parse_user(buffer, count, new_value); 368 if (!err) { 369 cpumask_copy(prof_cpu_mask, new_value); 370 err = count; 371 } 372 free_cpumask_var(new_value); 373 return err; 374 } 375 376 static const struct proc_ops prof_cpu_mask_proc_ops = { 377 .proc_open = prof_cpu_mask_proc_open, 378 .proc_read = seq_read, 379 .proc_lseek = seq_lseek, 380 .proc_release = single_release, 381 .proc_write = prof_cpu_mask_proc_write, 382 }; 383 384 void create_prof_cpu_mask(void) 385 { 386 /* create /proc/irq/prof_cpu_mask */ 387 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_ops); 388 } 389 390 /* 391 * This function accesses profiling information. The returned data is 392 * binary: the sampling step and the actual contents of the profile 393 * buffer. Use of the program readprofile is recommended in order to 394 * get meaningful info out of these data. 395 */ 396 static ssize_t 397 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos) 398 { 399 unsigned long p = *ppos; 400 ssize_t read; 401 char *pnt; 402 unsigned long sample_step = 1UL << prof_shift; 403 404 profile_flip_buffers(); 405 if (p >= (prof_len+1)*sizeof(unsigned int)) 406 return 0; 407 if (count > (prof_len+1)*sizeof(unsigned int) - p) 408 count = (prof_len+1)*sizeof(unsigned int) - p; 409 read = 0; 410 411 while (p < sizeof(unsigned int) && count > 0) { 412 if (put_user(*((char *)(&sample_step)+p), buf)) 413 return -EFAULT; 414 buf++; p++; count--; read++; 415 } 416 pnt = (char *)prof_buffer + p - sizeof(atomic_t); 417 if (copy_to_user(buf, (void *)pnt, count)) 418 return -EFAULT; 419 read += count; 420 *ppos += read; 421 return read; 422 } 423 424 /* default is to not implement this call */ 425 int __weak setup_profiling_timer(unsigned mult) 426 { 427 return -EINVAL; 428 } 429 430 /* 431 * Writing to /proc/profile resets the counters 432 * 433 * Writing a 'profiling multiplier' value into it also re-sets the profiling 434 * interrupt frequency, on architectures that support this. 435 */ 436 static ssize_t write_profile(struct file *file, const char __user *buf, 437 size_t count, loff_t *ppos) 438 { 439 #ifdef CONFIG_SMP 440 if (count == sizeof(int)) { 441 unsigned int multiplier; 442 443 if (copy_from_user(&multiplier, buf, sizeof(int))) 444 return -EFAULT; 445 446 if (setup_profiling_timer(multiplier)) 447 return -EINVAL; 448 } 449 #endif 450 profile_discard_flip_buffers(); 451 memset(prof_buffer, 0, prof_len * sizeof(atomic_t)); 452 return count; 453 } 454 455 static const struct proc_ops profile_proc_ops = { 456 .proc_read = read_profile, 457 .proc_write = write_profile, 458 .proc_lseek = default_llseek, 459 }; 460 461 int __ref create_proc_profile(void) 462 { 463 struct proc_dir_entry *entry; 464 #ifdef CONFIG_SMP 465 enum cpuhp_state online_state; 466 #endif 467 468 int err = 0; 469 470 if (!prof_on) 471 return 0; 472 #ifdef CONFIG_SMP 473 err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE", 474 profile_prepare_cpu, profile_dead_cpu); 475 if (err) 476 return err; 477 478 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE", 479 profile_online_cpu, NULL); 480 if (err < 0) 481 goto err_state_prep; 482 online_state = err; 483 err = 0; 484 #endif 485 entry = proc_create("profile", S_IWUSR | S_IRUGO, 486 NULL, &profile_proc_ops); 487 if (!entry) 488 goto err_state_onl; 489 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t)); 490 491 return err; 492 err_state_onl: 493 #ifdef CONFIG_SMP 494 cpuhp_remove_state(online_state); 495 err_state_prep: 496 cpuhp_remove_state(CPUHP_PROFILE_PREPARE); 497 #endif 498 return err; 499 } 500 subsys_initcall(create_proc_profile); 501 #endif /* CONFIG_PROC_FS */ 502